1. Field of the Invention
The present invention relates to a technique for detecting an inter-turn short circuit, more particularly, to a technique for detecting an inter-turn short circuit in a winding product.
2. Description of Related Art
There is a plurality of winding products in the market, for example, motors, transformers, etc. During a fabrication process of the winding product, scratching, breaking and chapping of an enameled film of a winding thereof are inevitable. Moreover, regarding devices with high using voltages, such as a high voltage ignition coil, an LCD inverter, an isolated flyback DC-DC converter, etc., after a period of utilization, spark discharges are probably generated due to inadequate isolation of the enameled wires, which may even cause a damage of the whole device. Therefore, it is a very important technique to detect whether or not an inter-turn short circuit is occurred in the winding of the winding product.
In the conventional technique, though a general inductance/capacitance/resistance LCR meter can measure electrical characteristics of a device, since a detecting voltage thereof is very low, the inter-turn short circuit phenomenon of the winding cannot be detected. Moreover, though a general Hi-pot tester can exert a high voltage to both ends of the winding, such method takes the winding as a load, which may cause more damage.
Moreover, when the motor is rotated, a current or a voltage signal of the motor is opportunely measured, and a power decomposition technique is used to obtain a negative sequence current. Then, a theoretical negative sequence current caused by unbalance of the motor itself is calculated, and after a deduction operation, a remained current value is caused by the inter-turn short circuit. However, according to such method, errors are generated during calculation and actual measurement.
Accordingly, a detecting technique using a pulse resonance is developed. Presently, the technique of detecting whether or not the inter-turn short circuit is occurred in the winding of the winding product according to the pulse resonance is regarded as the safest and the most reliable technique. Regarding a current pulse resonance tester, it first detects a voltage signal of the winding of the normal winding product to serve as a comparison party, and then measures a voltage signal of a winding of another winding product. Then, the measured voltage signal is compared to the voltage signal serving as the comparison party to determine whether or not the winding of the winding product to be detected is normal.
However, in the conventional technique, when an abnormal winding product is detected, a difference between the voltage signal of the abnormal winding product and the voltage signal measured from the normal winding product is probably tiny, and even cannot be distinguished by naked eyes. Therefore, in the conventional technique, an experienced inspector is required for determining whether or not the inter-turn short circuit is occurred in the winding. In other words, the conventional technique cannot be widespread, and a lot of human labour and cost are spent. Moreover, since the difference between the voltage signals is very tiny, during an inspection process of a large quantity of products, it can be carelessly neglected, which may lead to a result that the bad products pass through the inspection.